This study will determine whether somatostatin analogue Sandoz 201-995 is effective in suppressing hormone secretion by aggressive hypersecretory endocrine tumors. The somatostatin analogue, octreotide, is admimistered to patients with various types of hypersecretory endocrine tumors to determine the suppressive effect of this drug on hormone hypersecretion. Twenty-seven patients with neuroendocrine tumors such as ectopic ACTH, growth hormone producing tumors, growth hormone releasing hormone tumors and a cranial hemangiopericytoma causing hypophosphatemia have been studied to date.